import { useQuery } from "@tanstack/react-query";
import { fetchShift, type ShiftStatus, type TillId } from "../api.js";
import { qk } from "./query.js";

// Shared shift status for the whole app — the header control, the booth screen's
// per-shift log scope, and the pay/exit modal's gate all read this one Query so
// they never disagree about whether a shift is open and whose it is. A shift is a
// per-TILL single-open accountability period (at most one open per till). The
// default till is the booth; the wash desk reads its own (`useShift("carwash")`).
// The WS invalidates qk.shift (a prefix, so every till) on shift_open/shift_z_report/
// cash movements, so this stays live without polling. See wiki/concepts/shift.md.

export interface ShiftState {
  /** Raw status from the server (null while loading / on error). */
  status: ShiftStatus | undefined;
  /** Is a shift open on this till? */
  isOpen: boolean;
  /** Is the open shift the logged-in operator's (so they may close it / operate)? */
  isMine: boolean;
  /** A shift is open but belongs to someone else — this operator is blocked. */
  blockedByOther: boolean;
  /** ISO start of the open shift, for scoping the per-shift log. */
  startedAt: string | null;
  /** Whoever holds the open shift (for "held by X" messaging). */
  heldBy: string | null;
  isLoading: boolean;
}

/** Query key of one till's shift status — under the qk.shift prefix so the WS
 *  invalidation reaches every till. */
export const shiftKey = (till: TillId) => [...qk.shift, "current", till] as const;

export function useShift(till: TillId = "booth"): ShiftState {
  const q = useQuery({ queryKey: shiftKey(till), queryFn: () => fetchShift(till) });
  const s = q.data;
  const isOpen = s?.open != null;
  const isMine = s?.isMine ?? false;
  return {
    status: s,
    isOpen,
    isMine,
    blockedByOther: isOpen && !isMine,
    startedAt: s?.open?.startedAt ?? null,
    heldBy: s?.open?.operator ?? null,
    isLoading: q.isLoading,
  };
}